1. Field of the Invention
The present invention relates to turbo machines, and in particular relates to a turbo machine able to prevent instability in flow, by suppressing swirl due to recirculation flow at an inlet of an impeller and by suppressing rotation stalls of the impeller, irrespective of the types and the fluid thereof.
In more details, the present invention relates to the turbo machines, such as for a pump, a compressor, a blower, etc., having non-volume type impeller therewith, and in particular, relates to the turbo machine being able to prevent from the instability in flow, by suppressing a swirl or pre-whirl which is generated due to a main flow or component of the recirculation occurring at an inlet of an impeller and by suppressing rotation stalls thereof, thereby being suitable to be applied into a mixed-flow pump, which is used widely as water circulating pumps in a thermal power plant or in a nuclear power plant, a drainage pump, as well as, relates to a pump station into which is applied the turbo machine according to the present invention.
2. Description of Prior Art
Rotary machines being called by a name of "turbo machine" can be classified as below, depending upon the fluids by which the machines are operated and in types thereof.
1. With fluids by which the machine is operated: PA1 2. In Types: PA1 1. Casing treatment: PA1 2. Separator: PA1 3. Active control: PA1 a casing having a flow surface defined therein; PA1 an impeller having a plurality of blades and being positioned within said casing; PA1 a plurality of grooves being formed in the flow surface of said casing, for connecting between an inlet side of said impeller and an area in which the blades of said impeller reside, wherein each of said grooves is at least equal to 5 mm or greater than that in a width. PA1 a casing having a flow surface defined therein; PA1 an impeller having a plurality of blades and being positioned within said casing; PA1 a plurality of grooves being formed in the flow surface of said casing in radial direction thereof, for connecting between an inlet side of said impeller and an area in which the blades of said impeller reside in a gradient direction of fluid pressure therein, wherein each of said grooves is at least equal to 5 mm or greater than that in a width, and PA1 a terminal position at downstream side of each of said grooves is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of swirl at a terminal position of each of said grooves at upstream side thereof. PA1 a casing having a flow surface defined therein; PA1 an impeller having a plurality of blades and being positioned within said casing; PA1 a large number of shallow grooves being formed in the flow surface of said casing, for connecting between a spot where swirl is generated in a low flow rate of fluid at an inlet side of said impeller and an area in which the blades of said impeller reside in a direction of pressure gradient of the fluid, wherein each of said grooves is at least equal to 5 mm or greater than that in width thereof, and PA1 a terminal position at downstream side of each said groove is located in such a manner that fluid can be obtained under pressure being necessary to suppress generation of the swirl at a terminal position at upstream side of each said groove, thereby removing a behavior of uprising at the right-hand side from a head-flow rate characteristic curve of said turbo machine. PA1 an open-type impeller having a plurality of blades therewith; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein; PA1 a plurality of grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein: PA1 an open-type impeller having a plurality of blades therewith; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein; PA1 a plurality of grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein: PA1 an open-type impeller having a plurality of blades therewith; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein; PA1 a large number of shallow grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof and being equal or greater than 5 mm in depth thereof, for connecting between a spot where swirl is generated in a low flow rate of fluid at an inlet side of said impeller and an area on the interior surface of said casing in which the blades of said impeller reside in a direction of pressure gradient of the fluid, on a periphery thereof, wherein: PA1 an open-type impeller having a plurality of blades therewith; PA1 a casing having a conical wall surface therein and being positioned with said impeller therein; PA1 a plurality of grooves being formed in a direction of pressure gradation so as to project from the conical wall surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, wherein: PA1 an open-type impeller having a plurality of blades therewith; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein; PA1 a plurality of grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein: PA1 a closed-type impeller having a plurality of blades and a shroud thereabouts; PA1 a casing having a inner wall and being positioned with said impeller therein, wherein said impeller is formed into an open-type having no shroud thereabouts in vicinity of an inlet of said impeller; and PA1 a plurality of grooves in a direction of pressure gradient, being formed on the inner wall of said casing opposing to that portion in vicinity of the inlet of said impeller having no shroud thereabouts, on a periphery thereof, wherein: PA1 a closed-type impeller having a plurality of blades and a shroud thereabouts; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein, wherein said impeller is formed into an open-type having no shroud thereabouts in vicinity of an inlet of said impeller; and PA1 a large number of shallow grooves being formed in the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof and being equal or greater than 5 mm in depth thereof, for connecting between a spot where swirl is generated in a low flow rate of fluid at an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside in a direction of pressure gradient of the fluid, on a periphery thereof, wherein: PA1 an impeller having a plurality of blades therewith; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein; and PA1 a plurality of grooves being formed on the flow surface of said casing, opposing to an outer peripheral portion of said impeller at an inlet side of the blades thereof, for connecting between an inlet side of said impeller and an area on the flow surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein: PA1 an impeller having a plurality of blades therewith; PA1 a casing having a flow surface defined therein and being positioned with said impeller therein; and PA1 a plurality of grooves being formed in the flow surface of said casing, for connecting between an inlet side of said impeller and an area on the interior surface of said casing in which the blades of said impeller reside, on a periphery thereof, wherein an index of determining a form of said grooves is obtained by a following equation: EQU JE No.=WR.times.VR.times.WDR.times.DLDR PA1 where, WR (a width ratio) is a value obtained by dividing a total value of the groove widths W with a length of casing periphery; PA1 VR (a volume ratio) is a value obtained by dividing a total volume of said grooves with a volume of said impeller; PA1 WDR (a width-depth ratio) is a value obtained by dividing the width W of said groove with a depth D of said groove; and PA1 DLDR is a ratio between a length of said groove in flow, being lower than the impeller inlet and the depth of said groove, and wherein, said grooves are formed so that the index JE No. lies in a range from 0.03 to 0.5. PA1 a pump having an impeller and a casing being positioned with said impeller therein, for pumping up the fluid in the suction side; PA1 a passage for conducting the fluid being pumped up from said pump to the discharge side; PA1 a driver apparatus for ratably driving said impeller of said pump; and PA1 controller means for controlling rotation speed of said impeller of said pump, wherein said pump is the pump defined in the above.
Liquid, and Gas.
An axial flow type, a mixed-flow type, and a centrifugal type.
In FIG. 22 showing a cross-section view of a mixed-flow pump which is now mainly or widely used due to ease of operation. It comprises a suction casing 11, a pump 12 and a diffuser 13, in a sequence from upper stream to down stream thereof.
A blade (of an impeller) 122 rotating within a casing 121 of the pump 12 is rotationally driven on a rotary shaft 123, thereby supplying energy to the liquid which is suctioned from the suction casing 11. The diffuser 13 has a function of converting a portion of velocity (or kinetic) energy of the liquid into static pressure.
FIG. 23 shows a typical characteristic curve between head and flow rate of the turbo machine including the mixed flow pump shown in FIG. 22, where the horizontal axis shows a parameter indicating the flow rate, while the vertical axis a parameter indicating the head.
Namely, the head decreases in reverse relation to increase of the flow rate in a region of low flow rate, however it rises up following the increase of the flow rate during the time when the flow rate lies within a S region (i.e., a portion uprising or jumping up at the right-hand side in the characteristic curve). And, when the flow rate rises up further, exceeding the right-hand uprising portion of the characteristic curve, the head begins to again, following the increase in the flow rate.
Then, in a case where the turbo machine is operated with the flow rate of such the characteristic curve of uprising at the right-hand side, a mass of the liquid vibrates by itself, i.e., generating a surging phenomenon.
Such the characteristic curve of uprising at the right-hand side is caused, since the recirculation comes out at an outer edge of the inlet of the impeller when the flow rate flowing through the turbo machine is low, and at that instance, a flow passage or a channel for the liquid flowing into the turbo machine is narrowed, thereby generating a swirl in the liquid (see FIG. 22).
Since the surging gives damages not only upon the turbo machine, but also upon conduits or pipes which are connected to upper stream and down stream sides thereof, it is inhibited to be practiced in a region of low flow rate. Further, there were already proposed various methods for suppressing the surging as below, other than an improvement made in the shape (i.e., profile) of the blade, for the purpose of expanding or enlarging the operation region of the turbo machine.
Thin or narrow grooves or drains, being from 10% to 20% of a chordal length of the blade, are formed in a casing region where the impeller lies, so as to improve a stall margin.
FIGS. 24(a) and (b) show explanatory views of the casing treatment which were already proposed, in particular, FIG. 24(a) shows a positional relationship between the casing treatment and the blades, and FIG. 24(b) shows the cross section views of the casing treatment.
Namely, with the casing treatment which were already proposed, the grooves being sufficient in the depth are formed in an inner wall (i.e., flow surface) of the casing on the region where the blades lie, in an axial direction, in a peripheral direction, or in an oblique direction, alternatively, in a radial direction or an oblique direction, respectively.
Though is not yet investigated clearly the mechanism on how the casing treatment enables the improvement in the stall margin theoretically, it can be considered that because the fluid of high pressure is spouted out or injected into a low energy region and inhibits occurrence of the installing cells.
A separator is provided for dividing the recirculation flow occurring at the outer edge of the inlet of the impeller into a reverse flow portion and a forward flow portion (i.e., in a main flow direction), in the region of low flow rate, thereby prohibiting the expansion of the recirculation.
FIGS. 25(a)-(c) are explanatory views for the separators, each of which is applied to the turbo machine of the axial flow type, in particular, there are proposed a suction ring type (in FIG. 25(a)), a blade separator type (in FIG. 25(b)), and an air separator type (in FIG. 25(c)), respectively.
In the suction ring type (in FIG. 25(a)), the reverse flow is enclosed within an outside of the suction ring, and in the blade separator type (in FIG. 25(b)) is provided a fin between the casing and the ring. Further, with the air separator type (in FIG. 25(c)), a front end or a tip of the moving wing (i.e., the blade) is opened so as to introduce the reverse flows into the outside of the casing, thereby prohibiting the swirl from being generated due to the reverse flows by means of the fin. Thus, it is more effective, comparing with the former two types mentioned, however, comes to be large-scaled in the devices thereof.
This is to suppress the generation of the swirl due to the recirculation by injecting or spouting out the high pressure fluid from an outside into a spot where the recirculation occurs.
Furthermore, as an example of the conventional turbo machines, a mixed-flow pump will be described hereinafter. To a mixed-flow pump, it is required to show a head-flow rate characteristic curve (hereinafter, called by "head curve") having no behavior uprising at the right-hand side for enabling a stable operation, in a case where the pump is operated over the whole flow range thereof. However, ordinarily in a pump, it is common that the characteristics, such as an efficiency representing performance of the pump, a stability of the head curve, a cavitation performance, and an axial motive power for closure, etc., are in reversed relationships to one another. Namely, if trying to improve one of those characteristics, the other one(s) is is decreased down, therefore there is a problem that it is difficult to obtain improvements in at least two or more characteristics at the same time. For example, with a pump in which consideration was made primarily onto the efficiency thereof, the head curve shows a remarkable behavior uprising at the right-hand side in a portion thereof, thereby it has a tendency to be unstable.
For obtaining a head curve continuously falling down at the right-hand side for enabling the stable operation, in the conventional arts, as is mentioned in the above, it is already known that the casing treatment or the separator is provided or treated therein. Such the structure is already described, for example in U.S. Pat. No. 4,212,585.